Query based on direction

Question

Hi
Does anyone know if its possible to query data based on direction eg. select all objects that are east of object A.
Thanks
K

Answer 1

K
I quickly changed that function so it returns the direction (N, E, S, W) instead of the actual argument between two point geometries. So for polygons, I would take the centroid or a point_on_surface to evaluate the direction.
you could use it as follows.
select b.name, get_compas(SDO_GEOM.SDO_POINTONSURFACE(a.geometry, 0.05),
SDO_GEOM.SDO_POINTONSURFACE(b.geometry, 0.05))
from your_polygon_table a, your_polygon_table b
where a.id = YOUR_FILTER_ID
OR
select b.name, b.id
from your_polygon_table a, your_polygon_table b
where a.id = YOUR_FILTER_ID
and get_compas(SDO_GEOM.SDO_POINTONSURFACE(a.geometry, 0.05),
SDO_GEOM.SDO_POINTONSURFACE(b.geometry, 0.05)) = 'E'
Here is the raw function:
my_geometry1, my_geometry2 must be non-geodetic 2D points gemeotries
the function returns the direction (N, E, S, W) of the second point relative to the first
create or replace function GET_COMPAS
(my_geometry1 IN MDSYS.SDO_GEOMETRY, my_geometry2 IN MDSYS.SDO_GEOMETRY)
RETURN VARCHAR2 AS
my_XCoord2 REAL;
my_YCoord2 REAL;
my_XCoord1 REAL;
my_YCoord1 REAL;
pi CONSTANT REAL := 4 * ATAN(1);
my_DeltaX REAL;
my_DeltaY REAL;
my_Argument REAL;
my_TGOmega REAL;
my_Rotation REAL;
direction varchar2(1);
BEGIN
my_XCoord1 := my_geometry1.SDO_POINT.X;
my_YCoord1 := my_geometry1.SDO_POINT.Y;
my_XCoord2 := my_geometry2.SDO_POINT.X;
my_yCoord2 := my_geometry2.SDO_POINT.Y;
my_DeltaX := my_XCoord2 - my_XCoord1;
my_DeltaY := my_YCoord2 - my_YCoord1;
IF (my_DeltaY = 0) THEN
IF (my_DeltaX > 0) THEN
my_Argument := pi / 2;
ELSE
my_Argument := 3 * (pi / 2);
END IF;
ELSE
my_TGOmega := ABS(my_DELTAX) / ABS(my_DeltaY);
IF (my_DeltaX > 0) THEN
IF (my_DeltaY > 0) THEN
my_Argument := ATAN(my_TGOmega);
ELSE
my_Argument := pi - ATAN(my_TGOmega);
END IF;
ELSE
IF (my_DeltaY > 0) THEN
my_Argument := 2 * pi - ATAN(my_TGOmega);
ELSE
my_Argument := pi + ATAN(my_TGOmega);
END IF;
END IF;
END IF;
direction := case
when my_argument <= (pi / 4) then 'N'
when ((pi / 4) < my_argument AND my_argument < 3*(pi / 4)) then 'E'
when (3* (pi / 4) <= my_argument AND my_argument <= 5*(pi / 4)) then 'S'
when (5* (pi / 4) < my_argument AND my_argument < 7*(pi / 4)) then 'W'
when 7* (pi / 4) <= my_argument then 'N'
end;
return direction ;
END;
Edited by: lucvanlinden on Nov 16, 2008 10:49 AM